I'm a bit behind in my response, but the original question is why coconuts 
would not develop natural poisons like other seeds.  The answer is that 
developing natural poisons is one of several evolutionary strategies that 
seeds can adopt.  Another is to have a very hard shell.  The coconut with 
its natural husk is very hard for most animals to open.  So coconut is free 
from poisons.  In general, if you gathering food in the jungle, eat the nuts 
with the hardest shells.  They will be the safest.  Ken